Adam Fairbrass, 29, of Queen’s Way, Ipswich, and Trevor Summers, 28, of South Ockendon in Essex, were sentenced at Ipswich Crown Court to a total of 16 years in prison.
A man entered the Thelnetham Road shop in Hopton and threatened staff with a handgun and a knife on July 28 last year before making off on foot with cash reports a newspaper.
After a search of the area and speaking to witnesses, officers confirmed the man got into a maroon Toyota Previa and one of the other occupants of the car was a second man.
Following checks of CCTV images, a description of the offender being released and calls from further witnesses, information was received about a vehicle that may have been involved, belonging to Fairbrass.
Fairbrass, who was known to police, was arrested on August 6, 2010, with Summers.
Both men knew each other and while neither admitted their parts in the robbery in interview, it emerged the pair had gone shopping together in Essex just hours after the robbery was committed. The pair were released on bail.
Fairbrass was charged with conspiracy to commit robbery on January 26 while Summers, who was at that point remanded in custody for other matters, was issued with a summons for the same offence.
The pair were listed for trial at Ipswich Crown Court but pleaded guilty to conspiracy to commit armed robbery and today returned to court for sentencing of eight years each.
Senior investigating officer Superintendent Louisa Pepper said: “This incident was extremely frightening for the staff and customers of the Post Office, and caused great concern among the residents of this usually quiet village.
“A large police response was mobilised because of the actions of this pair and they are now facing a lengthy spell behind bars.
“This type of offence is extremely rare in Suffolk, and those who target community locations using unnecessary violence such as this can expect stiff penalties as we have seen today.”